GENEVA, Feb 15 (Reuters) - International mediator Lakhdar Brahimi said on Saturday the first two rounds of Syrian peace talks had not made much progress but that the two sides had agreed on an agenda for a third round at an unspecified date.

Brahimi said the last session of the second round of talks in Geneva was "as laborious as all the meetings we have had, but we agreed on an agenda for the next round when it does take place".

He said the points to be discussed included violence and terrorism, the transitional governing body, national institutions and national reconciliation.

However the mediator said the Syrian government wanted to first deal with the issue of combating terrorism and had refused to deal with any other points until that was resolved.

"I apologise that these two rounds have not come out with very much," he said.

The three-year-old Syrian conflict has killed more than 130,000 people and is destabilising the country's neighbours. The mainly Sunni Muslim rebels have drawn support from radical Sunni groups such as al Qaeda and other foreign militants.

Shi'ite countries and militias have thrown their weight behind President Bashar al-Assad, who is from Syria's minority Alawite sect, an offshoot of Shi'ite Islam.

Brahimi said both sides at the peace talks needed to reflect on their responsibilities. He said he hoped this would "lead the government side in particular to reassure us that when they speak of implementing the Geneva Communique they do mean a transitional governing body, exercising full executive power, will be the main objective". (Reporting by Oliver Holmes)